The present invention relates generally to a strut type suspension for an automotive vehicle, which is adapted to successfully prevent transmission of vibration or mechanical displacement between a wheel axle and a vehicle body. More specifically, the invention relates to a strut-type suspension which can prevent transmission of not only relatively low-frequency vibrations but also relatively high-frequency vibration.
In general, a strut-type suspension absorbs relative displacements between a wheel axle and a vehicle body so as to prevent transmission of vibrations, road shocks and so forth. The strut suspension generally includes a shock absorber for damping relative displacements between the wheel axle and the vehicle body. However, the shock absorber will not work successfully and satisfactory for relatively small-amplitude, high-frequency mechanical vibrations of the wheel axle or the vehicle body. Such short-stroke vibrations are absorbed by an elastic damper inserted between a strut assembly and the vehicle body. If such an elastic damper is relatively hard, suspension will be relatively rigid and so produce a relatively higher damping force for absorbing short-stroke vibrations. Such a hard elastic damper is good for damping relatively low-frequency vibrations to provide good driving stability but will give a rough ride. In addition, such a hard elastic damper will not adequately eliminate relatively high-frequency vibrations. In turn, when a relatively soft elastic damper is used, high-frequency vibrations will be successfully eliminated so that transmission of such high-frequency vibrations will be prevented. However, such a soft elastic damper will encounter a problem with respect to damping of relatively low-frequency vibrations which degrades driving stability and steering characteristics.
If an elastic damper such as a rubber bushing is designed for damping not only relatively low-frequency vibrations but also relatively high-frequency vibrations, the size of the damper has to be so large as to make same unsuitable for the strut assembly. Furthermore, in the case of a relatively soft elastic damper, the damper will be worn out in a relatively short period of time due to the relatively large deformations caused by every displacement cycle.
Therefore, in the prior art, it has been impossible, in practice, to achieve a damping effect sufficient to successfully and satisfactorily prevent transmission of vibrations due to mechanical displacements between the wheel axle and the vehicle body.